CDMAS ONLY: This is a genetic epidemiologic study that assesses risk factors for sleep apnea and directly measures sleep related breathing disorders in: 1) index probands identified through a sleep laboratory with diagnosed sleep apnea; 2) control probands (neighbors of #1); 3) the first degree relatives of #1 and #2. Subjects are restudied between 6 and 7 years later; a subsample (n=300) also is studied at 9-10 year follow up. The objectives of the project are: a) to characterize and quantitate the familial aggregation of sleep apnea and to identify the extent to which any observed familial aggregation is based on familial similarities in body habitus, ventilatory control mechanisms, anatomic risk factors, alcohol use, and allergy; b) to characterize the natural history of obstructive sleep apnea by assessing changes in the respiratory disturbance index (RDI) over a follow up period of 6-10 years; and c) to assess the relationship between hypertensive heart disease and sleep apnea. The GCRC CDMAS facility is assisting with a crucial data base conversion and updating for longitudinal follow up of 1500 subjects and is providing training support to the systems analyst on this project.